Telephone system



March 5, 1940. J, E. COLLYER TELEPHONE SYSTEM Filed July 6, 1937 INVENTOR. JOHN EDWARD COLLYER w O n A Patented Mar 1940 I era OFFICE TELEPHONE SYSTEM I "361 Edward Collyer, Stoke, Coventry, England, assignor to The General Electric Company,

, Limited, London, England ---Application July 6, 1937, Serial No. 152,103 U In Great Britain July 29, 1936' I .5 Claims. I (01177-380) vThe present invention,relatesnto telephone systems and more particularly to systems in which a substation connected to an automatic exchange is 'provided with special facilities for calling frequently wanted subscribers." With such arrangements certain predetermined numbers can be [selected by] a single operation.

I The object of the invention is the provision of improved arrangements for sending out trains of,

impulses'in'response to the vmomentary depression of a single key. l I

. Certain-systems for accomplishing this. purpose are known. For-examp1e, there isthetype'usually known as the mechanical keysender in which I I erated by a contact carried by the reed being of the correct ratio of make-to-break. The circuit theimpulses are created by the engagement of impulse con'tactsprings' with a-rotating cam.

shaped so as-to send a train of impulses characteristic of the-keydepressed. The power for driving the-rotating cam: is usually obtained from a wound up spring. In another'type usually known as an electrical keysenden-the depression of the key operates certain marking relays theic'ontacts of which are interconnectedwith the bank of a step-by-step switch which'rotates' at a uniform ratei Impulsetrains corresponding to the key depressed are'tran'smitted to'the line wires. I

The present invention belongs to the latter type andrelates to an improved keysender, which is particularly suitable foruse in association with public automaticexchanges. Such keysenders must be capable of accommodating a large number of codes, say 25 or' 50, and of sending out I I codes, containing a plurality oi trains of impulses The character of the impulssmust beat least equal to that obtained with the'dial switch usually associated with automatic telephone subscribers instruments. The present keysender is capable of fulfilling all'these' requirements 'yet 450 contains very little apparatus, is simple in op- 55; switch, which latter during rotation'controls the called subscribers.

emission of impulse trains over the subscribers line wires. The impulses sent out over the .line wires and also for driving the abovementioned second step-by-step switch are generated by a vibrator of the freelyvibrating type. The reed p of this vibrator has attached to it a Swedish iron mass, which iscapable of attraction. byfan electromagnet. Before the commencement of the train of impulses representing the first digit and between each train of impulses the electromagnet 10 is energisedso as to attract thereed and hold it stationary. When the reed is d e-energised it vibrates "freely at its own natural frequency (whichis, say, 10 per second), the impulsesgenarrangements are such that between each train of impulses there is a fixed pause of, say, 600 mini-seconds. n

In an'embodiment of my invention, a subscribers instrument is provided with a strip 0 ance with names or designations of frequently Depression of any one of these keys after removal of the subscribers re ceivercauses the operation of a start relay where upon the firststep by-step switch rotates by selfinterruption to find a point in its banks marked by the depressed key. When this point is reached the second step-by-step switch commences to 3 step under the influence of the vibrator as described above.

This second switch steps until it encounters amarking made in its banks by the first switch,

when impulsing ceases for a time suitable for an interdigital pause. The switch thenfcontinues to step until second and third markings are reached, impulses being transmitted meanwhile to the line wires. When the third marking is reached, a stop relay is operated which causes cessation of impulsing and returns the second switch to .a normal position; The wanted sub- I scriber has now been called and conversation may proceed in a normal manner.

number of impulses'in' a'train can be varied Furthermore, the number of trains of impulses in a code is only limited by the capacity of the second or sending switch. The usual type of stepfor example, twenty five keys labelled in accord- It will be seen thatby this arrangement the;

" a call is to be made.

by-step switch used in automatic telephone systems, containing 25 contacts in the half circle,

that is 50 contacts in the full circle, can by use of single-ended wipers be arranged to send as many as five digits in an impulse train, any or all of which may contain from one to ten impulses, I

In one form of the invention a call lamp is provided at the keysender which glows when the sender is in use. For the correct operation of the device it is necessary that all apparatus should be in its home or normal position before sending a code. Once a key is depressed the code can be cancelled by simply replacing the receiver on the switch hook, but the circuit arrangements are such that the depression of a further key will not be eifective until the apparatus has all returned to a normal condition. This is indicated by the lamp ceasing to glow.

A keysender according to the invention, al-

though described as for use by a subscriber having an ordinary telephone instrument, could of course be employed with equal facility by an operator situated at either a branch or a main ex-. change. If the operator is employed in connectionwith a private automatic branch exchange connected to' a public automatic main exchange, then the keysender can be switched into use for either setting up local calls to the private exchange or junction calls to the main exchange. Connection to the latter may be established either by directly connecting the keysender to the outgoing junction lines or by switching it temporarily into a cord circuit or the like.

In order that the nature of the invention may now be better understood reference should be made to the accompanying drawing which illustrates by way of example a circuit embodying the principles of the invention. 1

In the drawing a number of keys I, 2 are provided, and are fitted either in the base of a subscribers telephone instrument or in a box adjacent thereto. The remainder of the apparatus of the impulse sender consists of switches and relays, and if necessary a current supply unit operating from power supply mains, and this may be fitted in a single box or cabinet near the subscribers instrument.

The switch PS is the one employed to register a position corresponding to the key depressed when It has four banks of contacts, and if each bank contains 25 contacts, then a maximum of 25 codes can be sent, since the switch has no normal position. The switch DS which acts to control the emission of impulses, is

' provided with two banks only, bank DS! being a sector whilst bank DS2 has as many groups of ten contacts as the maximum number of digits involved in any code. In switches provided with 25 5' contacts per row, it is usual to connect a 25-point switch in such manner that each one of a pair of contact rows is associated with a single-ended 'wiper, these wipers being also connected in pairs such that the equivalent of a 50-point bank is correctly spaced impulses of suitable impulse ratio until the pendulum has lost most of its energy.

It proposed to describethe operation of the device by sending a typical code. Thus if key No. 1 is depressed, earth from contact H is removed from contact 5 of bank PSI and applied to relay S which operates. It is, of course, assumed that the subscriber has previously removed the receiver, establishing a loop from the exchange through contact R2 and the subscriber's instrument. On the operation of relay S sl prepares to operate relay K.

The switch commences to step to find the point in its bank from whichearth has been removed by key No. 1 andthis continues until its wiper PS! encounters a contact from Which'earth has been removed, this being caused'by operation of key No. 1. All other contacts in this bank are either connected to unoperated keys 'or are, permanently earthed. The earth for driving the I switch magnet being, now removed, relay Koperates in series with PSM from earth on ,-.tl

via sl,

kl locks relay K operated via'tLI k2 prepares to remove a short-circuit impulsing contact dl.

forfthe vi I k3 operates relay C and energises the magnet DSM of the. code sending switch. I This switch being of the reverse drive type does not yet move its wipers. I

The operated key is-now released, allowing relay S to'return to normal.

s2 allows theweight of the vibrator relay to release, and its contact opensand closes at a rate and ratio equal to that of the desired I I impulses, releasing andoperating relay D.

s3 and s4 prevent the reapplication of earth to the switch bank by theresto'red key No.1

from steppingthe switch PS. 1',

85 leaves the line loop under control of the impulsing contact .dl. 1

At the instant of opening of contact 85, contact all is closed, but a' short time later relay D 're leases at the commencement of the .first impulsedl opens the line loop. d2 releases the magnet DSM and allows the associated wipers to take one step. 1

When relay D operates at. the end of the im-:

pulse due to closure of the vibrator contacts, dl;

recloses the line loop and-d2 re -energises the magnet DSM, and the cycle is repeated. Assuming that the numbercorresponding to the depression of key No. l, is 375, then the fourth contact in bank DSZ is connected to the fifth contact in bank PS2. When the magnet DSM energises for the fourth time, i. e., at the end of the third impulse, earth via I03, 112, pal bank -DS2,; bank PS2 and contact cl operates relay P.

, pl energis'es themagnet M, thereby holding the vibrator contacts closed andthe relay D- operated. I p2 short-circuits pal. p3 de-energises relay leases slowly. f ploperates relay.PA.x

C, which, being slugged, re-

s2 energises the magnet M, pulling the weight When relay C finally releases, its contact cl de-energises relay P which also releases slowly.

When this latter action is complete,

pl de-energises the vibrator magnet and impulsing recommences.

, p3 re-energises relay C.

When contact (12 once more breaks, relay PA and the magnet DSlVi are both de-energised and release, and the transmission of a second impulse train is commenced. This impulse. train is terminated bya second marking which is applied to the bank BS2 from bank PS3. Since the digit to be transmitted is '7, this second marking is spaced seven contacts after the first, and an inter-digital pause is provided as previously described by means of the release time of relays C and P. Impulsing is then resumed to send the final impulse train of 5, at the end of which time the wiper D82 reaches a third marking and op erates relay T via bank BS4.

tl releases relay K. t2 short-circuits the impulsing contact 01!. it connects the magnet DSM to bank DSI through the contact springs-(is which cause the switch to step its wipers by self interruption to the first contacts in their banks. 7

t4 locks relay T operated to earth on wiper DSI. kl prepares to replace earth from H on the keys.

let releases relay C. v

The switch DS now rotates its wipers until they reach the home position, relay T remaining held untilthen. Whenstepping ceases, the circuit of relay T is broken by wiper DSl, and this relay releases, its contact 731 finally enabling further digits to be sent if required.

It should be noticed that the lamp EL, provided to show the subscriber that the impulse sender is transmitting, lights up immediately the subscriber releases the depressed button from earth derived from .vviper DSl. The lighting of this lamp warns the subscriber not to depress any further buttons nor to operate his own dial whilst the sender is impulsing. ;It should be-noticed that two rows .of terminals designated I? are provided between bank DSZ and the cooperating banks of the switch PS. These terminals form a translating panel, enabling the depression of any button tosend any desired code. nalson banks PS2, PS3 and- PS4 are wired to appropriately labelled terminals on the panel, as

also are the terminals of bank DS2. According to the digits to be sent by each key, jumper wires similar to those shown dotted are run between the two groups of terminals, this permitting easy setting up of any particular code, which may be changed'to another code if circumstances require.

Should the subscriber find, midway through the emission of a code, that the wrong number is being sent, the code can be cancelled by replacing the receiver, This breaks the line loop and releases any switches taken into use at the exchange. The keysender meanwhile completes its cycle of operations before returning to normal,

" the engaged lamp EL warning the subscriber not to attempt to set up a further code.

Should he do so bydepressing akey, it will be seen that since either contact 101 or t1 is operated, no earth is available to operate relay S, so

that the storage and sending cycle can'not'be All the termirepeated until the sender is in a normal condition, with all relays released and the switch DS suitablyipositioned.

I claim: I 1. In an impulse sender, a rotary switch, means for marking a plurality of consecutive or non consecutive contacts in the bank cfsaid switch, means operating at a predetermined speed, an impulse sending circuit including acontact set actuated periodically by said last means, a step ping circuit for. said switch including a contact set actuated periodically and in synchronism with the actuation ofsaid first contact set, and means operated over a wiper of-said switch when said wiper encounters each marked contact, thereby to interrupt, for an. interval of time, the operation of said second means and the actuation of said contact sets.

2. In an impulse sender, a rotary switch, means for marking a plurality of consecutive or non- 5 consecutive contacts in the bank of said switch, means operating at a predetermined speed, an impulse sending circuit including a contact set actuated periodically by said last means, a stepping circuit for said switch including a contact set actuated periodically and in synchronism with the actuation of said first contact set, means operated over a wiper of said switch when said wiper encounters certain of said marked contacts thereby to interrupt, for a predetermined interval I of time, the operation of said second means and the actuation. of said contact sets, and means if a operated over a wiper of said switch when said wiper encounters a marked contact'other than wsaid certain marked contacts thereby to render said first contact set ineffective without interrupting the operation of said second means.

3. In an impulse sender, a rotary switch having a normal position, two stepping circuits for said switch, means for marking a plurality of consecutive or non-consecutive contacts in the bank of said switch, a member vibrating at its natural frequency, an "impulsingcontact in one of said circuits, said contact controlled by said member to step said switch, means operated over a wiper or said switch when said wiper encounters each marked contact except. the last to interrupt, for an interval of time, the vibration of said member, and means operated over said wiper when said wiper encounters said last marked contact to interrupt said one stepping circuit and to render the other'stepping circuit efiective, said switch thereafter operating self-interruptedly in said other circuit until it reaches its norm'alposition.

4. In'an impulse sender as claimed in claim 3, an impulsing circuit including a second contact controlled by said member, and. means for shunting said second contact responsive 'to the-operation of said last means. f

' 5. In an impulse sender, a plurality of manually operable keys, a rotary switch, means for marking a plurality of contacts in the bank of said switch responsive to one operation of any one of said keys, an impulsegenerator operative responsive to a second operation of said one key so f and effective to rotate said switch step-by-step,

and-'means operated over a wiper ofsaid switch when said wiper encounters each marked contact thereby to interrupt the operation of said generator for a predetermined interval of time.

Jorm EDWARD coLLYER. 

